We will consider some of the reasons.
A. Suppose all believers are raptured after the tribulation. In that case we would not need to be watchful, waiting, or prepared because we are assured that the Lord will come after the three-and-a-half-year period. If so, I could do all manner of evil for three years, five months, and twenty-nine days. This contradicts a most important principle of the Bible.
B. If all are raptured after the tribulation, then our waiting is not a waiting for Christ. Instead, it becomes a waiting for Antichrist, because Antichrist comes first.
C. The church will lose its hope. Titus 2:13 says, "Awaiting the blessed hope," that is, the blessing of escaping the tribulation.
D. The second school does not admit that there is a secret rapture. They forget that the Lord said, "I will come as a thief." The thief comes in secret. He is not preceded by a military marching band. The thief comes to steal the best things.
E. Concerning the twelve disciples’ being Christians, the second school says that they were all Christians. This is exactly opposite to the first school, which says that none of them were Christians. But the fact is that while the twelve disciples were representatives of the Jewish remnant, they were at the same time Christians also. For example, in Matthew 10:5-6 and 23:3 all have a Jewish background. These verses do not refer to Christians.
F. Not differentiating the rapture (Christ’s coming for the saints) from the appearing (Christ’s coming with the saints). There is a public rapture. In the book of Jude the Lord’s coming, as referred to by Enoch’s prophecy, is a public rapture because He puts His feet on the Mount of Olives. Revelation 1:7 speaks of the same thing. But those who believe in only one public appearing are confused. They are of the historical school, which says that the only portion of Revelation left to be fulfilled is that portion after chapter seventeen. They are exactly opposite to the futuristic school, which says that only chapters one through three have already been fulfilled. If the events in the book of Revelation are the things of the past, then it is no longer revelation. Hence, this book would be understood only by scholars and historians and not by babes. Fulfillment in the Bible is usually literal. For example, the virgin Mary, Bethlehem, etc. are all literal. Occasionally there are fulfillments that are figurative, but they are explained at that time.
Let us look at the following:
A. Revelation 3:10: "Because you have kept the word of My endurance, I also will keep you out of the hour of trial, which is about to come on the whole inhabited earth." This is the great tribulation. This verse tells us that some people can escape the great tribulation because they have kept the word of endurance. This verse refutes both the first school and the second school. Although Philadelphia represents the true church in the age of grace, it is also only one of the seven churches in Asia at that time. Thus, we know that only a small number (one-seventh) can be raptured before the tribulation. Furthermore, the rapture before the tribulation is not based on regeneration, that is, on being merely children of God. It is based on one condition alone, and that is to keep the word of His endurance. May we ask, "Can all the believers today keep the word of His endurance?" From this, we know that not all can be raptured before the tribulation. The second school says that this verse does not refer to the rapture before the tribulation but to God’s preserving of us during the tribulation; it merely means that during the great tribulation God will lead us through the tribulation. This is just as if a house were on fire yet one room is spared the damage. Also, this is like the Israelites who did not suffer the plagues while in the land of Goshen. This is wrong!
(1) Here it is not to be kept through but to be kept from. In the original Greek, after the word for "keep" there is the Greek word ek, which means "out of" (for example, ekklesia— a called-out group). Hence, it is not a matter of being kept through, but of being kept out of. Ek means "out of." (2) "Because you have kept the word of My endurance, I also will keep you out of the hour of trial, which is about to come on the whole inhabited earth, to try them who dwell on the earth." ("Kept" and "keep" in the original text are of the same root.) The hour of trial is not the tribulation but the time of the tribulation. For example, I was in the northwest of Shanghai during the Sino-Japanese War. I was not hurt. This was God’s keeping me through that tribulation; it was not His keeping me from the hour of that tribulation. If we want to be kept from the hour, we must be kept out of this world. If God wants to keep us out of this world, there are only two ways: death and rapture. Those in Philadelphia have died already, so they are kept from the hour of the great tribulation. But God cannot kill today’s church just because He wants to keep it from the hour of the great tribulation. Hence, the only way is to rapture it.
(Collected Works of Watchman Nee, The (Set 1) Vol. 15: Study on Matthew, Chapter 26, by Watchman Nee)